Two US fighter jets have dropped bombs on the Great Barrier Reef after a training exercise went horribly wrong.

The planes jettisoned four bombs because they were low on fuel and could not land loaded, the US Navy said.

It had been intended to drop the bombs at a nearby bombing range, but the mission was aborted, the BBC reported.

To minimise damage, the US Navy said the AV-8B Harriers dropped the bombs in deep water away from coral to minimise damage to the World Heritage Site.

The jets were going to target a bombing range on nearby Townshend Island, Sky News said.

But that mission was aborted so the bombs were dropped off the coast of Queensland. None of them exploded.

The incident happened during a joint training exercise bringing together 28,000 US and Australian military personnel over a three-week period, The Times reported.